BP is to receive $4bn (£2.5bn) cash as part of a settlement with Anadarko Petroleum over last year's Deepwater Horizon oil platform disaster.
The money will go into a $20bn trust that BP set up to meet claims against it following the Gulf of Mexico oil spillage and deaths of rig workers.
Anadarko owned 25% of the oil well. Both companies have agreed to drop all other claims against each other.
Investors welcomed the news, with BP shares almost 5% up in early trading
BP chief executive Bob Dudley said the settlement was "clear progress" towards ending long-running legal disputes with it partners in drilling project, and he called on other contractors to seek a resolution.
BP is still in dispute with other contractors, including Transocean and Halliburton, involved in drilling the Macondo oil well.
An official report has blamed safety and operational lapses for the worst oil spill in US history and oil rig explosion which killed 11 workers.
Mr Dudley, BP's chief executive, said in a statement: "This settlement [with Anadarko] represents a positive resolution of a significant uncertainty and it resolves the issues among all the leaseholders of the Macondo well.
"There is clear progress with parties stepping forward to meet their obligations and help fund the economic and environmental restoration of the Gulf. It's time for the contractors, including Transocean and Halliburton, to do the same."
BP has recently struck settlements with MOEX, which owned 10% of the Macondo well, and Weatherford, which provided drilling equipment.
As part of the latest settlement, US-based Anadarko will drop its claims of gross negligence against BP and give up its 25% interest in the Macondo well.
BP will end claims for about $6bn of invoices against Anadarko, and also award the company a small share of any successful insurance claims or money recovered from third parties.
The out-of-court settlement involves no admission of liability from either side.